The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various structures and methods to produce differential amplifiers such as the differential amplifiers used for ECL and CML logic devices. In some cases, the differential amplifiers incorporated diode loads in the collectors of the differential pair transistors in order to improve the bandwidth of the differential amplifier. FIG. 1 schematically illustrates an example of a differential amplifier 100 that has diode loads 103 and 104 connected to the collectors of the differential pair transistors 101 and 102. However, the diode loads created a high impedance on the output 105 and 106 of the differential amplifier which degraded the bandwidth instead of increasing the bandwidth.
Additionally, the diode loads dropped voltage which reduced the amount of voltage available for use by the differential pair of the differential amplifier. The voltage drop also limited the use of the differential amplifier at low power supply voltage levels.
Accordingly, it is desirable to have a differential amplifier that has increased bandwidth, that has a lower output impedance, and that can operate at lower power supply voltage levels.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain NPN devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention.